Safety switch



July 2, 1940. L, E 2,206,324

- SAFETY SWITCH Filed March 5, 193B N VE N 70 R fkmm/ck 150M920 1 205 Patented July 2, 1940 UNITED STATES PATENT ()FFlCE SAFETY SWITCH Application March 5, 1938, Serial No. 194,144

1 Claim.

My invention relates to improvements in safety switches which are particularly adapted for use with oil burners. The object of the invention is to provide means whereby an increase or a decrease of pressure in the oil supply line between the pump and the burner will cause the switch to open and shut off the current to the motor which operates the pump. A still further object is to provide means whereby the burning of oil which may accumulate below the burner will break the electric circuit.

In oil burner installations, the presence of water in the oil supply line will cause a drop in pressure on the discharge side of the pump as soon as the water reaches the gears of the pump and dirt or other solid obstruction between the pump and the burner will increase the pressure, rendering the operation of the burner unsafe until the flow from supply to burner jet is rectified and it is with a view to shutting off the operation of the burner under unsafe conditions that the present invention is designed.

The invention consists essentially of a cylinder having a plunger, which plunger is movable 2 in response to abnormal pressure in a supply line, and a switch rockingly mounted upon a shaft adapted to be opened by the movement of the plunger from its normal position, as will be more fully described in the following speci- 30 fication and shown in the accompanying draw ing, in which- Fig. 1 is a front elevational view of the invention.

Fig. 2 is a sectional view taken on the line 35 2--2 of Figure 1.

Fig. 3 is a diagrammatic View showing the various switch positions.

In the drawing like characters of reference indicate corresponding parts in each figure.

40 The numeral l indicates a switch base consisting of a horizontal plate 2 and a back panel 3. Extending downwardly below the plate 2 is a cylinder 4 connected at its lower end by a pipe 5 to the supply line 6 of an oil burner of a furnace, not shown. A. plunger 1 having a connecting rod 8 is fitted within the cylinder and is provided with a spring 9 to force the plunger downward, the force of such downward thrust being adjusted by a nut ID at the head 50 of the cylinder.

is provided with a toothed rack H, the purpose of which will hereinafter appear A discharge outlet 1?. is provided adjacent the upper end of the cylinder 4, which is fitted 55 with a branch pipe l3 leading to a suitable point The upper end of the rod 8 of discharge, to relieve the cylinder of any fluid passing the plunger, or pushing the plunger beyond the branch pipe connection.

A knife switch l4, having a hingedly mounted blade 15, is supported upon the horizontal plate 5 2 and a lever I6 is pivotally mounted as at I! to extend through said plate to provide a lower portion l8, which is adapted to be connected by a cord l9 carried through the base of the furnace in such a position that it may be burned and the tension released in the event of abnormal heat or flame within the furnace. The upper portion 20 of the lever I5 is connected by an insulated link 2! to the free end of the switch blade and. a tension spring 22 is at- 15 tached to said upper lever portion to Withdraw the blade in case of rupture of the pull cord I9.

Extending forwardly from the back panel 3 are stub shafts 2s and 24. The shaft 23 is 20 fitted with a sleeve 25 to which is secured a pinion 25 in mesh with the toothed rack II and a gear 21 which engages a small gear 28 mounted upon a sleeve 28 upon the stub shaft 24; The sleeve 25 supports axially a clip 38 25 in which a mercury switch 3| is carried. The switch 3| is provided with two terminals 32 and 33, the enclosed ends of which are immersed to close the circuit, when in normal position as shown in Figures 1 and 2.

The switch circuit includes wires 34 and 35. The wire 34 connects with the mercury switch terminal 32, the wire 35 connects with the lower terminal 36 of the knife switch l4 and the mercury switch 3| is connected by a wire 31 to the 35 upper terminal 38 of the knife switch M. A reel 39 may be carried axially by the clip 30, upon which the wires 34 and 3'1 may coil and uncoil as the switch 3! is rotated.

A subsidiary push button switch, not shown, 40 is connected in parallel with the switch above described, which is used only to start the oil feed pump and bring up the pressure in the oil line to normal operating pressure.

The operation of the switch is as follows:

The normal operating pressure having been set up by the oil feed pump disposes the plunger 1 in the position shown in Figure l, the rack II will consequently project approximately half its length above and half below its contact with the pinion 2B and the mercury switch 3| will be in the position shown in Figures 1 and 2 and in the position shown in the Diagram B of Figure 3, in which the terminals 32 and 33 are immersed and the switch closed, so that the motor operating the burner will continue to run. Should a rise develop in the oil line 6 due to obstruction or any other defect in the system, the plunger 1 will compress the spring 9 and through the rack H rotate the gears 26, 21 and 23 to substantially invert the mercury switch 3! to the position shown in the Diagram A of Figure 3, thus uncovering the terminals and breaking the circuit to stop the burner from further operation.

If the pressure in the oil line drops below its normal range the gears 26, 21 and 23 will be rotated in the opposite direction and will invert the mercury switch substantially to the position in Diagram C of Figure 3, again breaking the circuit.

In the event of the pull cord l9 being burned and ruptured where it passes through the furnace, the tension of the spring 22 will open the knife switch i4 and cause the burner to cease to function.

What I claim as my invention is:

A safety switch adapted to be operated in response to fluid pressure consisting of a mercury switch element mounted upon a horizontal axis, a cylinder adapted for connection to a source of fluid pressure, a loaded plunger adapted to assume a predetermined intermediate position within the cylinder when the pressure to the cylinder is normal, said plunger having a connecting rod and a gear train operatively connecting the switch element with the connecting rod whereby any upward or downward movement of the plunger from its predetermined intermediate position in the cylinder will effect a movement of the switch element towards open position, said gear train including a toothed rack connected with the connecting rod, a gear in mesh. with the rack, a gear rotatable in unison with the first mentioned gear and a driven gear by which the mercury switch is rotated, said driven gear being rotated by the second mentioned gear.

FREDERICK LEONARD LADE. 

